首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   311951篇
  免费   35166篇
  国内免费   153篇
  2018年   3103篇
  2017年   3158篇
  2016年   3863篇
  2015年   4712篇
  2014年   5411篇
  2013年   7323篇
  2012年   8707篇
  2011年   8812篇
  2010年   5545篇
  2009年   5396篇
  2008年   7600篇
  2007年   7770篇
  2006年   7627篇
  2005年   10615篇
  2004年   10210篇
  2003年   8967篇
  2002年   6890篇
  2001年   17342篇
  2000年   17508篇
  1999年   13380篇
  1998年   3947篇
  1997年   4188篇
  1996年   3922篇
  1995年   3539篇
  1994年   3501篇
  1993年   3588篇
  1992年   10431篇
  1991年   10351篇
  1990年   9835篇
  1989年   9664篇
  1988年   9015篇
  1987年   8381篇
  1986年   7576篇
  1985年   7442篇
  1984年   5861篇
  1983年   5110篇
  1982年   3646篇
  1981年   3208篇
  1980年   3049篇
  1979年   5362篇
  1978年   4142篇
  1977年   3766篇
  1976年   3317篇
  1975年   3787篇
  1974年   3965篇
  1973年   3905篇
  1972年   3433篇
  1971年   3191篇
  1970年   2835篇
  1969年   2748篇
排序方式: 共有10000条查询结果,搜索用时 733 毫秒
991.
On 11 May 1985 the main stand of Bradford City Football Club caught fire. Within four minutes the stand was alight from end to end. Fifty three people were burnt to death and about 250 injured; 83 required admission to hospital, and 55 of these were treated by primary excision of their burns and skin grafting. In such disasters the help of staff from other hospitals and areas is essential. Patients should be assessed to see whether they have burns that will ultimately be fatal; if they have they should not be sent to regional burns units, where they would take up beds that could be used for patients with treatable burns. All districts should ensure that their plans for accidents in which burns injuries predominate are adequate.  相似文献   
992.
Two hybridomas secreting mouse cytotoxic monoclonal antibodies to in vivo and in vitro activated human T-lymphocyte and neutrophil surface membrane antigenic determinants have been produced. One of these monoclonal antibodies (Ta/H-2) appeared to be also specifically reactive to blast cells in the majority of non-T-non-B and T acute lymphoblastic leukemia patients.  相似文献   
993.
Ca2+ uptake and membrane potential in sarcoplasmic reticulum vesicles   总被引:2,自引:0,他引:2  
The rate of calcium uptake by sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle was stimulated by inside-negative membrane potential generated by K+ gradients in the presence of valinomycin. The increase in the calcium transport rate was accompanied by a proportional increase in the rate of calcium-dependent ATP hydrolysis, without significant change in the steady state level of the phosphorylated enzyme intermediate. Changes in the sarcoplasmic reticulum membrane potential during calcium transport were monitored with the optical probe, 3,3'-diethylthiadicarbocyanine. The decrease in the absorbance of 3,3'-diethylthiadicarbocyanine at 660 nm following generation of inside-negative membrane potential was reversed during ATP-induced calcium uptake. These observations support an electrogenic mechanism for the transport of calcium by the sarcoplasmic reticulum.  相似文献   
994.
995.
Flows of biomass and respiratory carbon were studied in a series of propylene-oxide sterilized soil microcosms. One-half of the microcosms received three pulsed additions of 200 ppm glucose-carbon to mimic rhizosphere carbon inputs. Biotic variables were: bacteria (Pseudomonas) alone, or amoebae (Acanthamoeba) and nematodes (Mesodiplogaster) singly, or both combined in the presence of bacteria.Over the 24-day experiment, respiration was significantly higher in the microcosms containing the bacterial grazers. Biomass accumulation by amoebae was significantly higher than that by nematodes. The nematodes respired up to 30-fold more CO2 per unit biomass than did amoebae. Similar amounts of carbon flowed into both respiratory and biomass carbon in microcosms with fauna, compared with the bacteria-alone microcosms. However, partitioning of available carbon by the microfauna varied considerably, with little biomass production and relatively more CO2-C produced in the nematode-containing microcosms. The amoebae, in contrast, allocated more carbon to tissue production (about 40% assimilation efficiency) and correspondingly less to CO2.  相似文献   
996.
997.
998.
999.
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号